An active matrix organic light-emitting diode (AMOLED) display device is a novel flat-panel display device. Due to a self-luminescent function of the OLED, no backlight source is required by the AMOLED display device. As compared with a liquid crystal display device, the AMOLED display device has a wider viewing angle and a higher contrast, as well as such advantages as a small size, a small weight and lower power consumption. In addition, a thin film transistor (TFT) is driven by a low direct current, so as to transmit a pixel voltage to the OLED for displaying, so the AMOLED display device further has an advantage of rapid response. Moreover, the AMOLED display device may be operated at a wider temperature range, and the production cost thereof is relatively low.
TFT may include p-Si TFT and a-Si TFT, with difference in the characteristics. Due to its own defect, e.g., a low on-state current, low mobility and weak stability caused by many defect states, the application of a-Si in many fields has been restrained. However, molecules of p-Si are arranged in one grain regularly and directionally, and the mobility of electrons is 200 to 300 times greater than that of the electrons in a-Si where the molecules are arranged irregularly, so p-Si has been widely used nowadays.
In the related art, a process for manufacturing the AMOLED includes steps of: depositing an insulating structure onto a pattern of an active layer, and forming a via-hole in the insulating structure so as to expose the active layer; and forming a source electrode and a drain electrode on the insulating structure, the source electrode and the drain electrode being electrically connected to the active layer through the via-hole.
When the insulating structure includes at least two insulating layers and the via-holes are formed in the insulating structure, it is required to etch these insulating layers simultaneously. Due to an uneven thickness of the layer and thereby an uneven etching degree, in order to ensure the formation of a first via-hole at each position on a glass substrate without any residual layer, usually the layer may be over-etched by, e.g., 40%. It means that, during the etching procedure, the active layer at the via-hole needs to be subjected to ion bombardment for a long period of time, which thus results in a rough surface of the active layer at the via-hole and an increase in the number of the defects. When the source electrode and the drain electrode are formed subsequently, a characteristic of the metal-semiconductor contact, and thereby an on-state characteristic of the entire TFT, will be affected adversely.